Canine Degenerative
Myelopathy (DM) is an adult-onset, progressive spinal cord disease
causing weakness in the hind limbs and eventually paraplegia. Dog
owners usually elect euthanasia within a year of diagnosis; however,
when euthanasia is delayed flaccid paralysis and widespread loss of
muscle mass occur. Because common acquired compressive spinal cord
diseases can mimic DM, a definitive diagnosis currently can only be
accomplished post-mortem by histopathologic observation of the
spinal cord.

Drs. Gary Johnson
and Joan Coates at the Animal Molecular Genetics Laboratory of the
University of Missouri and Drs. Claire Wade and Kerstin Lindblad-Toh
at the Broad Institute of MIT/Harvard and their colleagues have
identified a DNA mutation that is a major risk factor for
development of degenerative myelopathy in dogs. The research
project was funded by the AKC Canine Health Foundation, American
Boxer Charitable Foundation, Pembroke Welsh Corgi Club of America,
Rhodesian Ridgeback Club of the United States, French Bulldog Club
of America, and French Bulldog Rescue League.

A DNA test will
soon be available for breeders and pet owners,
along with information about what the test can and cannot tell
them. The test clearly identifies dogs that are clear (have 2
normal copies of the gene), those who are carriers (have one normal
copy of the gene and one mutated copy of the gene), and those who
are at much higher risk for developing DM (have 2 mutated copies of
the gene). However, having two mutated copies of the gene does not
necessarily result in disease.

Dogs that have
clinical signs or a presumptive diagnosis of DM have tested as
genetically affected. A relatively high percentage of dogs in
several breeds (including Boxers, Pembroke Welsh Corgis, Chesapeake
Bay Retrievers and Rhodesian Ridgebacks) have the predisposing
mutation. It is important to note that there are a large number of
dogs that have tested as genetically affected, but are reported as
clinically normal by their owners. It may be that many of these
dogs will develop clinical signs as they get older or that the
mutation will never manifest in these dogs. Research is still
needed to determine the frequency of the mutation in breeds known to
have DM (German Shepherd Dogs, Rhodesian Ridgebacks, Pembroke and
Cardigan Welsh Corgis, Boxers, Chesapeake Bay Retrievers). In the
future, we may identify other risk factors in those dogs that have
tested as genetically affected. Wise use of this test can reduce
the incidence of dogs at risk for DM in the long-term, particularly
if other low frequency risk factors are identified that can more
easily be reduced. It is likely to take many generations to reduce
the frequency of this disease in breeds with higher frequency of the
mutation. By contributing blood samples for testing this mutation,
owners will facilitate further study of the disease and the genetic
risk factors underlying it.

Additional research
funded by participating breed clubs and the AKC Canine Health
Foundation will help answer questions that remain. Information
about the benefits of this test, testing forms and instructions, and
suggestions for using the test to reduce the frequency of DM will
soon be available online in the DM section of www.CanineGeneticDiseases.net.